1. Technical Field
This invention relates to DC power adapters for powering electronic devices.
2. Description of the Related Arts
There are power systems in the art which allow a user to hook up a DC/DC adapter to an automobile outlet, to supply regulated DC power to power an electronic device, such as a notebook computer. Automobile outlets typically provide a DC voltage in a range between 11.0 and 14.1 Volts. Some power systems also allow the user to hook up the DC/DC adapter to an airplane output such as an EMPOWER system, EMPOWER being a line of products sold by Astronics Advanced Electronic Systems for providing power to aircraft seats. An EMPOWER system typically provides a DC voltage in a range between 14.5 and 15.5 Volts.
Accordingly, some DC/DC adapters can be used with both an automobile outlet and the EMPOWER system to provide a regulated DC power to the electronic device such as the notebook computer. Notebook computers often contain lithium ion batteries. Such batteries can be recharged when the notebook computer is hooked up to the DC/DC adapter. For example, if the user is in a car, the user can couple a DC/DC adapter to the notebook computer and to the cigarette lighter outlet to power the notebook computer. The batteries in the notebook computer will draw some of the DC power supplied to recharge the batteries of the notebook computer if they are low in power. Accordingly, the user can simultaneously use the notebook computer and recharge the batteries therein.
The user can also use the DC/DC adapter while on an airplane, by plugging the DC/DC adapter into the EMPOWER outlet. The EMPOWER outlet and the automobile outlets have different sizes and shapes. Accordingly, the user can directly plug the DC/DC adapter into the EMPOWER outlet, and can place a connector over the EMPOWER plug of the DC/DC adapter and then plug the connector into the automobile cigarette lighter outlet. When the user hooks the DC/DC adapter up to the EMPOWER outlet and then to the electronic device, the electronic device receives the regulated DC power. However, if the charging circuitry in the battery malfunctions, the battery can overheat or even catch on fire when recharging from an EMPOWER DC source. If the battery were to catch on fire while an airplane in which the emPlower outlet is located is flying, the fire would have the potential to cause the airplane to crash or cause substantial damage.
To address this problem, one system in the art provides a connector to connect between the DC/DC adapter and the notebook computer to inform the notebook computer not to recharge the batteries. FIG. 1 illustrates a power supply system according to the prior art. As shown a DC power source 100 is coupled to a DC/DC adapter 105 via a cable 102. The DC/DC adapter 105 receives power from the DC power source 100 and outputs regulated DC power to an electronic device 120, via a cable 110 and a connector 115 coupled to the end of the cable 110.
The DC/DC adapter 105 can provide three output pins to the electronic device 120, as shown in FIGS. 2A and 2B of the prior art. The first pin can provide the output voltage (i.e., Vout), the second pin can provide a ground reference (i.e., GND), and the third pin can provide a data line (i.e., Vdata) to instruct the notebook as to whether the batteries should be recharged or not. For example, as shown in FIG. 2A, Vdata could be tied to GND to indicate that the DC power source 100 is the EMPOWER system and therefore the battery should not be recharged. Alternatively, as shown in FIG. 2B, Vdata could also be left open (i.e., to provide a non-grounded floating voltage) when the DC power source 100 in a cigarette lighter outlet of an automobile. Accordingly, when using the DC/DC adapter 105 while in an automobile, the user would use a connector 115 having the Vdata line floating, and when using the DC/DC adapter 105 with the EMPOWER system of an airplane, the user would use a connector 115 having the Vdata line tied to GND.
However, problems arise when the user forgets to change replace the connector 115 for use with the automobile when the user is in an airplane. Accordingly, if the user has the wrong connector 115 attached when using with the EMPOWER system, a battery of an electronic device 120 such as a notebook computer can charge the battery even when used with the EMPOWER system, and if the charging circuitry of the battery malfunctions, overheating or even a fire can occur, resulting in damage to the notebook computer. Also, if the connector 115 is damaged or flawed, then it may not provide the correct Vdata signal to the notebook computer, allowing the notebook computer to recharge the batteries in an airplane when they shouldn't be allowed to do so.
Accordingly, current DC/DC power adapter systems are deficient because they are incapable of automatically and intelligently informing an electronic device 120 coupled thereto of the DC power source (i.e., the EMPOWER system or an automobile cigarette lighter outlet).